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‘ilnited States Patent 0
3,019,837
Patented Feb. 6, 1962
2
1
In formations which are impermeable or slightly per
meable, fracturing can be utilized to provide suitable
channels for passage of air thru the stratum to effect the
3,019,837
IN SITU COMBUSTION PROCESS
John W. Marx, Richard H. Langenheim, Henry 0. Dixon, 7
and Joseph C. Trautham, all of Bartlesville, Okla,
assignors to Phillips Petroleum Company, a corpora
tion of Delaware
.
No Drawing. Filed Oct. 28, 1957, Ser. No. 692,592
8 Claims. (Cl. 166—11)
desired absorption of Oz.
The ?ow of air thru the formation can be continuous
or intermittent as the oxygen is rather quickly absorbed
by the carbonaceous material. When the section of the
formation adjacent the ignition borehole is substantially
saturated with 02, this section of the formation is heated
This invention relates to a process for recovering hydro 10 by any suitable means, such as by burning a mixture of
fuel gas and oxygen adjacent the wall of the borehole
containing the carbonaceous material or by an electric
tion. A speci?c aspect of the process is concerned with
heater or other suitable means, and when the temperature
an improved process for initiating in situ combustion in
of the formation adjacent the borehole reaches a mini
a carbonaceous stratum.
The recovery of oil by in situ combustion from carbo— 15 mum of about 450° F. and preferably 500 to 600° F.,
injection of air into the formation is commenced and
vnaceous strata is coming into wider use in the petroleum
ignition of the carbonaceous material is effected. A pre
industry. In this production technique, an area of the
ferred method of initiating the combustion comprises
formation is heated to combustion supporting tempera
injecting air into the surrounding boreholes so that the
ture by any suitable method and combustion is initiated
air passes thru the stratum to the ignition borehole,
by contacting the hot stratum with an oxygen-containing
causing the ignition of the hot carbonaceous material
gas such as air or oxygen-enriched air. Because of the
surrounding the ignition borehole, and effecting move
high heat capacity of the stratum and the heat transfer
ment of the resulting combustion zone radially outwardly
characteristics thereof extended periods of heating, such
from the ignition borehole countercurrently to the flow
as several days and even weeks, are usually required to
bring a section of the formation up to the ignition temper 25 of air so that the combustion zone passes thru the stratum
to the injection boreholes.
.
ature of the carbonaceous material therein. The ignition
If the injection of air is continued after the combustion
temperature can be lowered by utilizing pure oxygen or
zone arrives ‘at an injection borehole the movement of
oxygen-enriched air, but this of course increases the cost
carbons from a carbonaceous stratum by in situ combus
of recovery.
-
the combustion zone is reversed and it passes back thru
The principal object of the invention is to provide an 30 the formation, feeding on the carbonized residue therein
e?fected in the ?rst burning stage, until the combustion
improved process for effecting oil recovery from a car
zone ?nally arrives at the ignition borehole. In strata
bonaceous stratum by in situ combustion. Another ob
which are highly permeable, it is feasible to initiate com
ject is to provide an improved process for initiating in
bustion in the ignition borehole by direct injection of air
situ combustion in a carbonaceous stratum. A further
object is to reduce the time required for initiating in situ 35 and continuing the injection of air thru this borehole so
It is also an
as to movethe combustion zone by direct drive to the
object of the invention to increase the O2 availability in
surrounding boreholes. It is also feasible to initiatecom
bustion by direct air injection thru the ignition borehole
and after a substantial section of the stratum around the
combustion in a carbonaceous stratum.
carbonaceous stratum for initiation of in situ combustion
therein and for moving the combustion zone thru the
stratum. Other objects of the invention will become ap 40 borehole has been heated up to the range of 1,000 to
l,500° F. or higher in temperature, the ?ow of direct air
parent when considering the accompanying disclosure.
can be cut off and inverse air, injected thru the surround
It has been found that natural, porous tar sands, oil
ing boreholes, can be utilized to continue the combustion
sands, and shales made permeable by fracturing methods,
and move the combustion zone thru the formation to the
or naturally permeable, absorb 02 when air or other free
‘
oxygen-containing gas is injected into such strata. This 45 surrounding boreholes.
The absorption process is non-exothermic or only
phenomenon has been observed when air injected into a
mildly exothermic, indicating that oxygen is merely held
stratum has been found to be de?cient in oxygen when the
in solution in the hydrocarbon, Field data indicate that,
air is withdrawn or released from the formation. Labo
if sufficient residence time is allowed, more than 90 per
ratory tests con?rm this observation that oxygen is selec
tively absorbed from the air by native tar sands. When 50 cent of the oxygen can be removed from air by passing
air thru a permeable carbonaceous stratum. This oxygen
in situ burning of carbonaceous material in a stratum is
is then available to assist, and possibly to completely sus
effected after injecting air into the stratum prior to the
tain active combustion of the carbonaceous material when
initiation of combustion, as much as 3% CO2 in excess
temperatures are subsequently raised to the ignition point.
of that theoretically possible from the oxygen content
The invention is not limited to tar sands alone but is
of the air has been found in the combustion gas recovered, 55
applicable to shales, Athabasca sands, oil sands, etc., if
the additional 02 coming from absorbed oxygen present
the stratum is permeable or has been made permeable by
in the stratum before the combustion takes place.
fracturing methods or by acid treatment or other suit
The process of the invention comprises contacting a
able means. The method of the invention is more ef
carbonaceous stratum with free oxygen, such as with air,
so as to effect substantial absorption of 02 by the stratum, 60 fective in strata containing non-liquid hydrocarbons than
in strata containing a large proportion of the hydrocarbon
thereafter heating the stratum in the area of the absorbed
material in liquid form.
.
oxygen to a combustion supporting temperature and,
To
illustrate
the
invention,
boreholes
were
drilled in
while the stratum is at such temperature, contacting the
a tar sand in a conventional 5-spot pattern, with the corner
65 wells 10 feet apart and the ignition well at the center of
initiate combustion of the carbonaceous material with
the pattern. Air was injected thru the corner wells at a
same with a suitable free-oxygen containing gas so as to
the aid of the absorbed oxygen. In order to effect the
contacting of the stratum with free-oxygen an ignition
total rate of about 2,000 cubic feet per hour and passed
thru the formation to the ignition well. The formation
borehole is drilled thru the stratum and one or more sur
was about 10 feet in thickness. The ?rst air recovered
rounding boreholes are also drilled therein so that air 70 from the ignition borehole had an oxygen content in the
can be passed laterally thru the stratum, either from the
range of 10 to 11 percent and after about 16 hours of
ignition borehole or from the surrounding boreholes.
flow the absorption of oxygen was substantially com
amass?
plate, as the oxygen content of the withdrawn air was
normal. Laboratory’ tests indicate‘ that this tar sand
absorbs oxygen until its weight increases by about 3
percent. After saturation of the tar sand was complete,
the flow of air was terminated, temporarily, and the wall
of the ignition bore-hole was heated by a burner positioned
in the borehole opposite the carbonaceous stratum by
burning a mixture of propane and air therein. When
the stratum surrounding the burner was brought to a com
4
tacting same with a free»oxygen-containing gas so as to
initiate combustion of said carbonaceous material with
the aid of the absorbed oxygen.
2. The process of claim 1 wherein air is passed thru
said stratum to said borehole from at least one other bore
hole to effect said absorption and after said stratum is
heated, air injected thru said other borehole is_utilized
for initiating said combustion so that the combustion zone
advances counter-currently .to said air.
’
3. The process of claim 1 wherein ‘air’ is injected into
bustion supporting temperature, the how of air from the 10
said stratum thru said ignition borehole to effect said
corner wells was again initiated and the combustion of
the carbonaceous material was immediately initiated so
that the resulting combustion Zone moved slowly thru
the stratum toward the injection wells. Hydrocarbons
produced during the in situ combustion were recovered
from the ignition well by conventional methods.
In the pattern described above, time for saturation of
absorption.
4. The process of claim 1 wherein said contacting is
with continuously moving air.
5. The process of claim 1 wherein said contacting is
with stagnant air during a substantial portion of the con
tacting time.
6. The process of claim 1 wherein air in intermittently
injected into said stratum.
nition borehole will vary with different strata as to the
7. A process for initiating in situ combustion in a per
character of the carbonaceous materials and the per 20
the stratum between the injection boreholes and the ig
meable stratum containing carbonaceous material which
comprises injecting air into said stratum at a plurality of
points around a'nignition' borehole and forcing said air
either continuous or intermittent, since oxygen is ab
thru said stratum to said borehole; continuing the con
sorbed from stagnant air but, after the oxygen content of
the air is depleted or substantially’ reduced, more e'?icient 25 tacting of saidstratum with air until at least a substantial
section of said stratum around said ignition borehole is
absorption is obtained by introducing fresh air. The in
saturated with O2‘; thereafter, heating said stratum ad
vention is not limited to the spacing described in the
jacent said borehole to combustion supporting tempera
above illustration but may be varied as to the number of
ture; while said stratum is at said temperature, contacting
injection wells‘ as well as to the distance between the
ignition well and the injection wells. It is to be under 30 same with air so as to initiate combustion therein; and
continuing injection of air at said points so as to move
stood that the saturation of the carbonaceous material in
the resulting combustion zone thru said stratum toward
the stratum with oxygen not only aids the initiation of
said injection points.
combustion but also enhances the combustion process
8. A pieces for initiating in situ combustion in a per
as the combustion front moves thru the stratum.
Certain modi?cations of the invention will become 35 meable stratum containing combustible carbonaceous ma
terial which comprises passing air thru a section of said
apparent to those skilled in the art and the illustrative
meability of the strata. This time usually ranges from
about 10 to about 100 hours.
The how of air can be
details disclosed are not to be construed as imposing
stratum between a ?rst well and second well therein‘ so
unnecessary limitations on the invention.
as to effect absorption of 02 by said stratum; continuing
the passing of air thru said stratum for at least 10 hours
and until the 02 concentration in the ef?uent gas is sub
We claim:
‘
1. A process for initiating in situ combustion in a
permeable stratum containing carbonaceous material
which comprises contacting said formation adjacent an
ignition borehole therein with a fr'ee-oxygen-containing
gas so as to effect substantial absorption of 02 by said
stratum and withdrawing gaseous e?iuent from said 45
stantially that of the injected air; thereafter igniting said
stratum around one of said wells to establish a combus
tion zone in the adjacent stratum; and moving said com
bustion zone thru said stratum between the wells by
feeding air thereto.
stratum comprising contacting gas; continuing contacting
of said stratum with said gas for a, period of at least 10
hours and until the concentration of O2 in the e?iuent gas
References Cited in the ?le of this patent
UNITED STATES PATENTS
from the contacted stratum is substantially the same as
in said gas initially; thereafter heating said stratum ad 50
jacent said borehole to a combustion supporting tempera
ture; and while said stratum is at said temperature, con
2,793,696
Morse ______________ __. May 28, 1957
2,862,557
Van Utenhove et al _____ __.. Dec. 2, 1958
2,917,112
Trantham et al. ______ __ Dec. 15, 1959